1. Field Of The Invention
The present invention relates to a novel process for preparing a granular rubber and an apparatus for preparing the same.
2. Description Of The Prior Art
Heretofore, rubber has been used in the form of blocks or chips of certain desired sizes for the molding of rubber objects. In molding processes which use blocks of rubber, the blocks are cut and weighed and kneaded with a Banbury mixer or by roller mixing. However, because the rubber blocks are relatively large and because their sizes are not constant, the blocks are difficult to handle and precise weighing of the blocks is difficult. Because of these problems, it has been difficult to automatically weigh and process the rubber, thus requiring much labor to process the rubber.
Recently, various thermoplastic resins have been blended with rubber increasingly in enlarging fields of application. However, in the molding of rubber materials, it has been difficult to feed the rubber chips continuously at constant speed to a molding machine such as a uniaxial extruder or a biaxial extruder, and consequently, batch-type kneading methods have been employed. Batch type kneading techniques, however, have had the disadvantages of requiring long blending periods for the blending of the rubber with resins which increases the cost. Accordingly, it has been proposed to prepare granular rubbers which can be easily weighed and handled without trouble and can be fed at constant rates to a molding machine such as a uniaxial extruder or a biaxial extruder. In this technique, rubber blocks are formed by the adherence of rubber pellets to themselves because of the tackiness of the rubber pellets, even though pellets of rubber are prepared. Therefore, it has been difficult to obtain the desired objectives by this technique.
A need, therefore, continues to exist for a method by which granular rubber can be fed easily and conveniently to a molding apparatus.